A wide variety of mechanisms have been utilized to deploy panels from a storage container into some desired geometric patterned panel or array. Typically, such systems are used to deploy radio or radar antennas, solar-cell panel arrays for space craft, solar reflectors, etc. Some existing mechanisms for example utilize telescoping booms of circular or rectangular cross-section which support a flexible panel stored on a drum, and as the drum unwinds the panel is deployed between the two telescoping booms in a window shade manner.
Another mechanism utilizes telescoping booms and stores the panel in an accordion folded pack, deploying the panel between the booms in a similar manner to accordion pleated household drapes being drawn across a window. Other systems use inflatable booms or structures to support an array. In another, accordion folded panels are deployed by applying torque to each of the many panel hinges by means of a run-around cable and pulley system having drums located at each hinge point. In such arrangements, the panels are only coplanar upon full deployment, and should the system jamb during deployment the panels would be in a zig-zag patterned array. An exception is the earlier described drum deployment system which would have a portion of the window shade array deployed coplanar and usable should the deployment not be totally completed.
Many mechanisms and apparatus for actuating these systems utilize complex and heavy scissor arms, while others use springs for powering the deployment. Springs are heavy for the amount of power they supply, and additionally they do not provide the capability of retracting and restowing the array. In order to control the rate of deployment, dash pots are used in conjunction with the springs on some systems, thus reducing even more the power efficiency of the springs.
At least one of the inflatable structures utilizes a thermal setting resin to reinforce the structure and give it a permanent set once it has been deployed, and in still another refinement there is a metallizing of the inflatable structure after deployment. Clearly such systems are not capable of retraction and restowing.
A device having a deployment and retraction system overcoming the previously described limitations was disclosed in our U.S. Pat. No. 4,015,653, issued Apr. 5, 1977. Disclosed in said patent was a deployable structure having a foldable panel strip comprised of a plurality of rectangular panels hinged edge-to-edge in such a way that the panels could be folded in accordion fashion to provide a flat stack of minimum stowage volume. The invention utilized panels that optimized the cantilever and torsional mass stiffness properties of the system by employing lighter first-deployed panels than the last-deployed panels, eliminated reliance on spring energy and force balances, and employed a fully positive, fully engaged deployment mechanism.
The deployment mechanism utilized two deployment arms, each arm hinged at one end to the stowage compartment and having a second hinge partway along its length to permit folding it into a stowable length. A crawler, fitted around the outside diameter of each deployment arm in a telescoping manner, moved along the full length of the deployment arm by means of motor driven pinions engaging a rack on the deployment arm. The crawler carried the first panel with it as the crawler traversed the length of the deployment arm. Subsequent deployment of panels was accomplished by a second set of motor driven sprockets mounted on the crawler and engaged in perforations along the edges of each panel, the deployed strip comprised of a plurality of panels advancing much like a film strip in a movie projector.
To retract the deployed strip, a creaser bar extending across the bottom of the strip in a lateral direction under the hinge line of two adjoining panels was raised to jack-knife this pair of panels sufficiently to permit the panel edge engaged sprockets to drive the next pair of panels toward the creaser bar, and in so doing cause the jack-knifed pair of panels to fold compactly together in a back-to-back position in front of the stowage container. A shutter was utilized to capture each pair of folded panels and move them into the container where they were retained by a convoluted snake spring.
The panel driving sprockets were powered by electric motors connected to the sprockets by means of slip clutches, and shaft encoders were employed to obtain relative positions of the mechanisms for processing by flip-flop logic to properly sequence the operations of the creaser and shutter relative to panel positions.